The present invention relates to a degassing device of a fluid flowing in a heat exchanger and, in particular, in a radiator which is part of the cooling circuit of a motor vehicle engine.
It is known that the presence of air bubbles in the cooling fluid of an internal combustion engine can be the cause of "hot points" appearing in the engine cylinder head and resulting in deterioration and destruction risks of some parts of the engine due to an inefficient cooling.
For avoiding such disadvantages, means for "trapping" said air bubbles and preventing them from circulating through the cooling circuit and from possibly gathering at some points of the engine cylinder head have already been proposed.
In particular in a heat exchanger with tubes, one of said known means provides, in a water box of the radiator and on either side of a partition wall, a collecting chamber in which emerge the exchanger tubes and a compensation chamber adapted for being partially filled with fluid and communicating on the one hand with the collecting chamber at the lower portion of the wall and on the other hand with the outer atmosphere at its upper portion (filled with gas) through overpressure and/or depression valves. The upper portion of said compensation chamber is also in communication with the collecting chamber via a degassing port formed in said partition wall.
In operation, the air of gas bubbles carried by the fluid gather at the upper portion of the collecting chamber and from there pass directly through said port into the compensation chamber where they are "trapped" due to the depression created in said chamber by the pump circulating the cooling fluid.
However, it has been found that when the engine is being stopped, the gases which are confined in the compensation chamber tend to flow back via said port into the collecting chamber and into the upper tubes of the nest, and can then reach the engine cylinder head if the latter is placed at a level higher than that of the radiator, hence the risk of "hot points" appearing when restarting the engine. Moreover, when the compensation chamber contains a detector of the fluid minimum level, the operation of said detector can be disturbed by a fluid jet penetrating into said chamber via said port.